1. Field of the Invention
The present invention relates to an apparatus for changing the wiping range of a wiper for wiping a window of a vehicle such as an automobile.
2. Description of the Related Art
In a wiper of the above-described type, it is generally desirable that the wiper blades be stopped, when not in use, at a position as low as possible so that the wiper blades do not obstruct the view. The stop position, however, cannot be too low because an extremely low stop position involves the following disadvantage. In winter, when snow deposits on the portion of the vehicle where the stop position is located, the snow may hinder the movement of the wiper blades moving toward the stop position, thereby causing the wiper to be subjected to unnecessarily heavy load. This can lead to breakage of various members of the device, such as the wiper blades, the wiper arms, wiper link rods and the wiper motor.
In order to meet the requirements, a structure has been proposed, for instance, in Japanese Patent Laid-Open No. 59-47560, in which the wiping range within which the wiper arm oscillates can be changed by varying that end of the range including the stop position (without causing any substantial variation in the other end of the range which includes the reversal position). In this structure, in order to change the wiping range, a second link is capable of swinging displacement relative to a first link. However, in order to prevent any unwanted swinging displacement, the second link must be held in position by screws. This means that an operation of changing the wiping range requires the use of tools, the opening of the bonnet, etc, and it is therefore troublesome and complicated. Thus, the proposed structure fails to provide easy operation.
In view of this drawback, it is advantageous to cause the swinging displacement of the second link by utilizing the force of a spring extended between relatively displaceable points of support, one of which is a movable point of support on the swingable member. However, in order to prevent any undesired change in the wiping range, the spring must have strong resilient force. This means that the mechanism for supporting the spring must be correspondingly reinforced. Because this requirement is inconsistent with making the device light and compact, the use of a spring cannot easily be adopted.